1. Field of the Invention
The present invention relates to azo dyes useful in the dyeing of synthetic fibers, particularly aromatic polyester and metallized polypropylene fibers. More particularly, the invention relates to azo dyes prepared from, as a coupling component, the condensation product of 2,4-dihydroxybenzoic acid and 2 -aminopyridine.
2. Description of the Prior Art
Among polyester fibers, those based on polyethylene terephthalate continue to be the most important, although fibers based on 1,4-dimethylenecyclohexane terephthalate have become commercially available. Developments in both homo- and copolyesters have continued and many modified versions of polyethylene terephthalate have recently appeared on the market. With the advent of new fibers, the search is continuing for dyes which build up on the various types of polyester fabric proportionate to the amount of dye applied, and which are characteristized by good light and excellent sublimation properties.
Additionally, there is a need for dyes which will provide dyeings of good fastness properties on other synthetic fibers such as cellulose acetate, nylon and metal-modified, or metal-containing, polypropylene. Dyes for metallized polypropylene are becoming of particular importance in view of the increasing use of these fibers in carpeting.
Azo dyes, generally, are known for use in the dyeing of synthetic fibers. Azo dyes which possess hydroxy groups, however, although often having good sublimation fastness properties on polyester, frequently show a bathochromic coloration on nylon. Thus, for example, the dye of the formula ##STR2## shows good sublimation fastness on polyester, but is not of strong commercial importance because the slight mark-off onto nylon in the standard sublimation test is redder in shade than the dyed polyester, as is the nylon stain in the standard wash fastness test.
Accordingly, it is an object of the present invention to provide azo compounds and dyes which do not exhibit the bathochromic coloration phenomenon when used to dye polyester and which provide dyeings on synthetic fibers, particularly polyester and metallized polypropylene, having good dyeing and fastness properties.
This and other objects will be apparent from the following summary and description of preferred embodiments.